This invention is related to a device for relative movement of two elements comprising an arrangement for forming a connection between a first link arrangement and a movement arrangement, the movement arrangement being provided between the connection arrangement and one of the elements whereas the first link arrangement is provided between the connection arrangement and a second of the elements.
The relative movement of the two elements has the purpose to position them mutually in a manner aimed at by means of the force-applying arrangements. More specifically, the device according to the invention is intended to form a manipulator or robot. The second of the elements is intended to carry, directly or indirectly via a carrying arrangement, or constitute a working member to execute the function aimed at, for instance picking, placing, packing and palletising. However, it is remarked that the working member may be adapted to carry out also other work operations than those just mentioned. The first element may according to a first embodiment form a base member secured in space but could according to a second embodiment form at least a part of a carrier movable relative to a base member. A force-applying arrangement then serves for adjusting the position of the carrier relative to the base member.
A robot of the kind defined by way of introduction is described in U.S. Pat. No. 4,976,582. For the positioning of the second element, the robot comprises three force-applying arrangements, which in unison comprise three force-exerting members arranged in a triangular distribution on the first element. Each of the force members is connected to the movable second element via its own connection comprising two link arrangements and an intermediate connection arrangement. These three connections coupled in parallel are like-wise arranged in a triangular distribution. Each of these connections comprises a first link arrangement including two first links pivotably connected to the second element and a second link, which is rigidly connected to a movable portion of the force-exerting member and which by means of a connection arrangement is connected to the two first links. The second link is movable with regard to one single degree of freedom relative to the stationary portion of the power-exerting member. The connection arrangement connects the first and second links in a hinged manner with two but not more than two degrees of freedom. The link arrangement formed by the first links is connected to the second element so that two but not more than two degrees of freedom occur. In reality, the first link arrangements form parallelogram-shaped four-links systems. A disadvantage with this known type of robot is that it becomes comparatively bulky as a consequence of the triangular distribution discussed herein above. The angle between planes of pivoting of two adjacent second links must, namely, always be less than 180xc2x0. Thus, it is very difficult to arrange two or more of those robots closely to each other without collision. A further disadvantage is that it is structurally difficult to design the known robot with the required stiffness and strength since the movable portions of the three power-exerting members project in a star-like fashion from the first element, which with regard to the space requirement should be formed as small as possible but which on the other hand must be able to receive the power-exerting members. Thus, this means that it becomes difficult to design arms rigidly connected to the movable portions of the power-exerting members with a sufficient width as far as the arms themselves are concerned as well as their bearings at the first element.
A further disadvantage is that all arm lengths must be equal. This means that it is not possible to optimize the robot to the pattern of movement in question. Performance will always be symmetrically distributed in a symmetrical working area, which is not cost efficient.
Furthermore, the known robot cannot execute a tilt movement of the second element to fetch objects located sidewardly of or above the robot.
In addition, 3 further motors are required in order to change the inclination of the second element. It would be desirable to manage this will only 1 extra motor in order to achieve a cost-efficient concept.
As a consequence of the equilateral triangular construction of the known robot it is also difficult to arrange to work horizontally above conveyors, loading pallets etc. Furthermore, it should be mentioned that if a working member on the second element is to be driven by means of a motor on the first element, an axle extending between the first and second elements must comprises a torque-transmitting coupling allowing variation of the length of the axle. In practice, the axle is suitably designed as consisting of two axle parts, which are displacable telescopically relative to each other and the torque transmission of which is ensured by splines, wedge grooves or similar. This complicates the embodiment and makes the same more costly.
This invention aims at devising routes to develop the device of the kind defined by way of introduction so as to eliminate or at least reduce one or more of the disadvantages mentioned herein above. According to a sub aspect, the aim is to provide a greater flexibility as to the design of the device so that two or more devices may be placed to work comparatively close to each other. According to another sub aspect, an improved mobility of the robot is aimed at.
The object of the invention is achieved in that the first link arrangement comprises links pivotably connected relative to the connection arrangement and the associated of the elements via joints, that the movement arrangement is adapted to allow a relative movement between the connection arrangement and the associated of the elements, and that the device comprises force-applying arrangements to actuate the link arrangement and the movement arrangement so as to change the relative position between the elements.
Thus, the link arrangement forms an interconnection between the connection arrangement and the associated of the elements by means of at least two and preferably three links. This creates possibilities for an asymmetrical design of the device according to the invention and, accordingly, an adjustment of the working area thereof to its purpose. For instance, this asymmetrical character of the device according to the invention provides possibilities for a very dense packing of a plurality of robots. This differentiates the device according to the invention from the device according to U.S. Pat. No. 4,976,582, where a triangular structure with equal sides is aimed at and where in any case the angle between the planes of pivoting of two adjacent second links always must be less than 180xc2x0.
It is according to an embodiment possible to design the displacement arrangement as a second four-links system. In such cases the first and second four-links systems will, accordingly, be coupled in series to each other via the connection arrangement. This provides the device with very favourable operational qualities. A particularly advantageous option resides in the second four-links system being possible to use for achieving tilting of the working member by means of a force-applying arrangement comprising one single force-exerting member.
The use of two four-links systems coupled in series via the connection arrangement involves, in addition, in case the four-links systems are designed as parallelograms, that it is made possible to achieve force transmission via axles provided in the four-links systems and with assistance of cardan joints, angular gears and the like without having to introduce, in the axle sequence, any sliding couplings or similar intended to operate axle length compensating.
According to a preferable embodiment of the invention, the movement arrangement is designed as a pivot arm.
Several preferable developments of the invention are defined in the dependent claims. These developments and advantages in connection with the invention are dealt with more specifically in the following description.